This invention relates to fluorescent lamps and more particularly to fluorescent lamps having reduced sputtering effects. Still more particularly, it relates to mounts for such lamps.
Fluorescent lamps are energy efficient light sources. An arc discharge occurring in the lamp generates actinic radiation, which causes fluorescence from a contained phosphor coating on the interior of the lamp. The electron source is generally a metal coil, usually tungsten, containing an electron emissive material. Two such coils are provided, one at either end of an elongated glass tube. During operation of the lamp it is not unusual for sublimation or sputtered products from the coils to plate out on the inside surface of the lamp adjacent the coils, causing undesired darkening of the glass, reduced light output and limited life.
Prior techniques suggested for reducing the effects of sputtering have included application of shields or coating of portions of the emissive coil with glass or refractory material. For example, U.S. Pat. No. 2,769,112 suggests coating all of the interior metal parts, except the cathode, with a suspension of zirconium oxide or other refractory insulating oxide. These techniques are difficult to employ and are, therefore, uneconomical.
It would be an advance in the art to provide an efficient, economical means for reducing or eliminating such sputtering.
It is, therefore, an object of the invention to obviate the disadvantages of the prior art.
It is another object of the invention to reduce sputtering and the inherent loss of brightness caused thereby.
These objects are accomplished, in one aspect of the invention, by a mount for a fluorescent lamp that comprises a glass base with spaced-apart lead-in wires extending from therefrom. A longitudinal electrode coil containing an emitter material is mounted upon and extends between the lead-in wires. A coating of zinc oxide is provided on the ends of the electrode coil and upon the lead-in wires at least in the area where the electrode coil is mounted.
The use of this invention substantially reduces sputtering of the coil materials and thereby increases the useful life of the lamp. Further, it is simple and inexpensive to apply.